Having mastered all the elements of the project for a while, I decided to secure the communication between the three servers (loraserver, lora-app-server and join server) in TLS.
after finishing the configuration, that indicated here loraserver-certificates, I checked all the files, directories and paths. and it seems to me correct.

my folder “loraserver-certificates” is in"etc"

LORA SERVER ( join-server ) :

# Network-server API
# This is the network-server API that is used by LoRa App Server or other
# custom components interacting with LoRa Server.
[network_server.api]
# ip:port to bind the api server
bind="0.0.0.0:8000"
# ca certificate used by the api server (optional)
ca_cert="/etc/loraserver-certificates/certs/ca/ca.pem"
# tls certificate used by the api server (optional)
tls_cert="/etc/loraserver-certificates/certs/loraserver/api/server/loraserver-api-server.pem"
# tls key used by the api server (optional)
tls_key="/etc/loraserver-certificates/certs/loraserver/api/server/loraserver-api-server-key.pem"

# Settings for the "internal api"
# This is the API used by LoRa Server to communicate with LoRa App Server
# and should not be exposed to the end-user.
[application_server.api]
# ip:port to bind the api server
bind="0.0.0.0:8001"
# ca certificate used by the api server (optional)
ca_cert="/etc/loraserver-certificates/certs/ca/ca.pem"
# tls certificate used by the api server (optional)
tls_cert="/etc/loraserver-certificates/certs/lora-app-server/api/server/lora-app-server-api-
server.pem"
# tls key used by the api server (optional)
tls_key="/etc/loraserver-certificates/certs/lora-app-server/api/server/lora-app-server-api-server-
key.pem"